1. Technical Field
The present invention relates generally to metal screening masks applicable to processing of semiconductors and packaging of electronic components. More specifically, the present invention relates to metal masks and their structure, wherein the structure includes a layered configuration comprising a copper layer sandwiched between layers of nickel-cobalt alloy.
2. Related Art
Metal masks are used as stencils to form patterns for many applications that include fabrication of wiring layers for organic and ceramic type substrates and deposition of solder pastes. For such applications, materials are transferred through openings in metal masks onto alumina and glass-ceramic green sheets and onto organic substrates. The metal masks are formed by an electroplating process and are called electroformed (EFM) masks. Unfortunately, the electroformed masks, which comprise a copper core that is electroplated with nickel, are limited in ultimate tensile strength (UTS).
Thus, there is a need for a mask that has a higher ultimate tensile strength than exists in the prior art.